Nevada Test Site National Emission Standards for Hazardous Air Pollutants Calendar Year 2007

Abstract

The Nevada Test Site (NTS) is operated by the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office. From 1951 through 1992, the NTS was operated as the nation's site for nuclear weapons testing. The release of man-made radionuclides from the NTS as a result of testing activities has been monitored since the first decade of atmospheric testing. After 1962, when nuclear tests were conducted only underground, the radiation exposure to the public surrounding the NTS was greatly reduced. After the 1992 moratorium on nuclear testing, radiation monitoring on the NTS focused on detecting airborne radionuclides which come from historically contaminated soils resuspended into the air (e.g., by winds) and tritium-contaminated soil moisture emitted to the air from soils through evapotranspiration. To protect the public from harmful levels of man-made radiation, the Clean Air Act, National Emission Standards for Hazardous Air Pollutants (NESHAP) (Title 40 Code of Federal Regulations [CFR] Part 61 Subpart H) limits the release of radioactivity from a U.S. Department of Energy facility (e.g., the NTS) to 10 millirem per year (mrem/yr) effective dose equivalent to any member of the public. This is the dose limit established for someone living off of the NTS from radionuclides emitted to air from the NTS. This limit does not include the radiation doses that members of the public may receive through the intake of radioactive particles unrelated to NTS activities, such as those that come from naturally occurring elements in the environment (e.g., naturally occurring radionuclides in soil or radon gas from the earth or natural building materials), or from other man-made sources (e.g., medical treatments). The NTS demonstrates compliance using environmental measurements of radionuclide air concentrations at critical receptor locations. This method was approved by the U.S. Environmental Protection Agency for use on the NTS in 2001 and has been the sole method used since 2005. There are six critical receptor locations on the NTS that are actually pseudocritical receptor locations because they are hypothetical receptor locations; no person actually resides at these onsite locations. Annual average concentrations of detected radionuclides are compared with Concentration Levels (CL) for Environmental Compliance values listed in 40 CFR 61, Appendix E, Table 2. Compliance is demonstrated if the sum of fractions (CL/measured concentrations) of all detected radionuclides at each pseudo-critical receptor location is less than one. In 2007, as in all previous years for which this report has been produced, the NTS has demonstrated that the potential dose to the public from radiological emissions to air from current and past NTS activities is well below the 10 mrem/yr dose limit. Air sampling data collected onsite at each of the six pseudo-critical receptor stations on the NTS had average concentrations of nuclear test-related radioactivity that were a fraction of the limits listed in Table 2 in Appendix E of 40 CFR 61. They ranged from less than 1 percent to a maximum of 20 percent of the allowed NESHAP limit. Because the nearest member of the public resides approximately 20 kilometers (12 miles) from the NTS boundary, concentrations at this location would be only a small fraction of that measured on the NTS.